(a) Technical Field
The present invention relates to a display device and a method of controlling a touch detection unit thereof.
(b) Related Art
Conventional liquid crystal display (LCD) devices include two display panels having pixel electrodes and a common electrode, respectively, and a liquid crystal layer having an anisotropic dielectric interposed between the two display panels. The pixel electrodes are arranged in a matrix and connected to corresponding switching elements such as thin film transistors (TFTs) that may be sequentially applied with data voltages. The common electrode is disposed over the entire surface of the display panel and may be applied with a common voltage. The liquid crystal layer interposed between the pixel electrode and the common electrode constitutes a liquid crystal capacitor. The liquid crystal capacitor together with the switching element connected thereto serves as a basic unit of a pixel.
In such liquid crystal display devices a voltage is applied to the two electrodes to generate an electric field in the liquid crystal layer. The intensity of the electric field may be adjusted to control transmittance of light passing through the liquid crystal layer, so that a desired image can be obtained. In order to prevent degradation of the liquid crystal layer caused by long-term application of the electric field in one direction to the liquid crystal layer, polarities of data voltages with respect to the common voltage may be inverted for each frame, row, or pixel.
Touch screen panels may be attached to liquid crystal display devices to detect the touch (or contact) of a user's finger, touch pen, or stylus and the position of the touch to facilitate the writing or drawing of characters or images, or to detect the touching of an icon to cause a machine such as a computer to execute desired commands. However, such configurations can be costly due to the cost of the touch screen panel and the additional process of attaching the touch screen panel to the liquid crystal display device. Such configurations may also result in a deterioration in luminance of the liquid crystal panel and an increase in thickness of the liquid crystal display device.
Sensing elements constructed with thin film transistors or variable capacitors built into the display region of liquid crystal display devices may be used as a substitute for touch screen panels. The sensing elements detect changes in light or pressure on a screen so as to detect the touch of a user's finger or the like on the screen and the position of the touch.
However, the signals from the sensing elements built into the liquid crystal display device need to be processed to determine whether a touch has occurred and the position of the touch on the selecting units, and to adjust a driving voltage to allow the levels of the sensing signals (that vary with changes in the panel of the liquid crystal display device or surrounding environments) to be in a desired range. In such cases, a processor such an advanced RISC machine (ARM) may be used. Unfortunately, such processes may consume large amounts of power when accessing memory or generating driving clock signals.